Fix Wechat QRcode bug

[WanliZhong]

Merged with test: opencv/opencv_extra#1060

This PR is based on #3479 and #3480 , and also fixes #3478

Thanks @zihaomu, @Konano and @GZTimeWalker.

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• I agree to contribute to the project under Apache 2 License.
• To the best of my knowledge, the proposed patch is not based on a code under GPL or another license that is incompatible with OpenCV
• The PR is proposed to the proper branch
• There is a reference to the original bug report and related work
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  Patch to opencv_extra has the same branch name.
• The feature is well documented and sample code can be built with the project CMake

[GZTimeWalker]

Maybe we should use a more decent test case instead of "KFCVW50"? 😂

[Konano]

This can also trigger the issue.

The decoded message is I love OpenCV!!!

[zihaomu]

Maybe we should use a more decent test case instead of "KFCVW50"? 😂

I think that's Ok.